Cells ingest foreign molecules through the process of endocytosis, in which the foreign material is taken into the endosome and then digested before being released into the cell. The activity of therapeutic molecules may depend on their release from the endosome before digestion. Techniques used to rupture endosomes include bursting through osmotic swelling, bursting through photodynamic radiation, bursting by the thermal swelling of a polymer, bursting through the phase change of a polymer (coil to rod transformation), destabilization of endosomal membrane by surfactants carried into the endosome with the drug or gene.